Where sound travels quickest ?

Starting from the rest , a body P travels with a uniform acceleration of 4m/s^2 and starting from rest from the same point 4s later , a body Q travels with a uniform acceleration of 16m/s_2 in the same direction as P . Find when and where they meet .

Why do sound wave travel through longer distance during night than during day?

If the wavelength of the sound waves is halved the frequency ____.(doubled)